#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>

//#define SERVER_IP "127.0.0.1"
//#define SERVER_PORT 8889
#define SERVER_IP "192.168.220.130"
#define SERVER_PORT 9986
#define MSG_STR "Hello, Unix Network Program World!"

int main(int argc, char **argv)
{
int conn_fd = -1;
int rv = -1;
char buf[1024];
struct sockaddr_in serv_addr;

conn_fd = socket(AF_INET, SOCK_STREAM, 0);
if(conn_fd < 0)
{
printf("create socket failure: %s\n", strerror(errno));
return -1;                                                   //为什么要有返回值？为什么要返回-1而不是0？如果返回值能终止程序运行，那>不用关闭文件吗(不用goto到关闭文件处吗？)？
}

memset(&serv_addr, 0, sizeof(serv_addr));
serv_addr.sin_family = AF_INET;                          //如果我不知道服务器的信息怎么办？
serv_addr.sin_port = htons(SERVER_PORT);
inet_aton( SERVER_IP, &serv_addr.sin_addr );

if( connect(conn_fd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
{
printf("connect to server [%s:%d] failure: %s\n", SERVER_IP, SERVER_PORT, strerror(errno));
return 0;
 }

 if( write(conn_fd, MSG_STR, strlen(MSG_STR)) < 0 )
 {
 printf("Write data to server [%s:%d] failure: %s\n", SERVER_IP, SERVER_PORT, strerror(errno));
 goto cleanup;
 }

 memset(buf, 0, sizeof(buf));
 rv = read(conn_fd, buf, sizeof(buf));
 if(rv < 0)
 {
 printf("Read data from server failure: %s\n", strerror(errno));
 goto cleanup;
 } else if( 0 == rv )
 {
 printf("Client connect to server get disconnected\n");
 goto cleanup;
 }
 printf("Read %d bytes data from server: '%s'\n", rv, buf);


 cleanup:
 close(conn_fd);
 }
